Olefin oxides, such as propylene oxide, are important and versatile intermediates used in the production of a large variety of valuable consumer products such as polyurethane foams, polymers, alkylene glycol, cosmetics, food emulsifiers and as fumigants and insecticides.
Previous research on olefin epoxidation involved the use of Ag-based catalysts (Appl. Catal. A. Gen. 2001, 221, 73.), as well as silica supported Cu (J. Catal. 2005, 236, 401), various metal oxides (Appl. Catal. A. Gen. 2007, 316, 142), Au-based catalysts with H2 as a co-reactant (Ind. & Eng. Chem. Res. 1995, 34, 2298, J. Catal. 1998, 178, 566; Appl. Catal. A. Gen. 2000, 190, 43; Angew. Chem. Int. Ed. 2004, 43, 1546), titania based catalysts that deactivated quickly (Chem. Commun. 2001, 1356; Catal. Commun. 2003, 4, 385), molten salts of metal nitrates (Appl. Catal. A. Gen. 2000, 196, 217), the use of O3 (Appl. Catal. A. Gen. 2000, 196, 217) and nitrous oxide (Ind. & Eng. Chem. Res. 1995, 34, 2298) as reactants. Although these developments are scientifically interesting, they have serious drawbacks, such as low PO selectivities and/or low propylene conversions, short catalyst lifetimes, the use of higher pressures or the use of costly co-reactants (Appl. Catal. A. Gen. 2007, 316, 142).
As to a process for producing olefin oxides, olefin epoxidation in the presence of a metal-based catalyst has been proposed. For example, US2003/0191328 mentions a process for the epoxidation of hydrocarbon with oxygen in the presence of a mixture containing at least two metals from the specific metal group on a support having a specific BET surface area. JP2002-371074 mentions a process for producing an oxirane compound which process uses a metal oxide catalyst containing at least one metal selected from the metals belonging to the Group III to XVI of the periodic table.